Measuring and control system



5 Sheets-Sheet l 3nnentor JOHN F. LUHRS Ottorneg March 7, 1944. J. F. LUHRS I MEASURING AND CONTROL SYSTEM Filed Sept. 21, 1940 March 7, 1944. J. F. LUHRS MEASURING AND CONTROL SYSTEM 5 Sheets-'She et 2 Filed Sept. 21, 1940 QQN JOHN F. LUHRS v gi' r jm.

attorney FIG. 3

March 7, 1944. J. F. LUHRS MEASURING AND CONTROL SYSTEM Filed Sept. 21, 1940 5 Sheets$heet 3 JOHN F. LUHRS Fla 4 Gttomeg March 7, 1944. I J LUHRS "2,343,619

MEASURING AND CONTROL SYSTEM Filed Sept. 21, 1940 5 Sheets-Sheet 4 ZSnventor JOHN F. LUHRS e 5 Mme y March 7, 1944. LUHRS 2,343,619

MEASURING AND CONTROL SYSTEM Filed Sept. 21, 1940 5 Sheets-Sheet 5 3nventor JOHN F. LUHRS f (Ittorneg Q1. The generation or formation of vaporjgoi' the Liberationifoi 3. MolecularT Patented 7, 1944 PATEN r OFFICE msuamo sun comer. srs'rm John I. m", 01mm Heights, om, munor to Bailey Meter Delaware Company, a corporation of Application September 31, 1940, Serial No. 357,787 11 Claims. (01. 122-448) This. invention relates to the m of determining the relative or absolute magnitude of a variable,

and particularly to the determination of a variable such as the density of a .fluid in the vapor, liquid, or vapor-liquid phase. It will be apparcut that my invention may be used to determine the relation between like or unlike physical variables, such as pressures, temperatures, etc.,or to determine the proportion between abstract variables, such as numbers or mathematical functions.

More particularly my invention relates to a method 01' an apparatus for determining the density of a flowing fluid at a-particular point in its flow path, and further to the determination of the mean density of a flowing fluid'through a particular section of its flow path.

Such determinations as my invention gives may be used in the control oi a variable directly or in-. directly through regulation of an agent or agents producing, maintaining, or otherwise affecting the variable, or it may be used to give a visual indication thereof.

I have chosen to illustrate and describe as a preferred embodiment of my invention its adaptation to the measuring and controlling of the density and other characteristics of a flowing heated fluid stream, such as the flow of hydrocarbon oil through a cracking still.

While a partially satisfactory control oi the cracking operation may be had from a knowledge of the temperature, pressure, and rate of flow'of the fluid stream being treated, yet a knowledge of the density of the flowing stream at diiIerent points in its path is of a considerably greater value to the operator, but was not available prior to the discovery by Robert L. Rude, as claimed in his copending application Serial No. 700,485.

In the treatment of water below the critical pressure, as in a vapor generator, a knowledge of temperature, pressure and rate oi flow may be sumcient for proper control, inasmuch as definite tables have been established for interrelation be tween temperature and pressure, and from which tables the density of the liquid or vapor may be determined. However, there are no available tables for determining the density of a hydrocarpetroleum liquid, Whether or not separation from the liquidocc f r K issolved or entrained gases.

arrangement as by cracking: or

polymeri tion. an

Ihe result is that no temperature-pressure density tables may be established for any liquid,

vapor, or liquid-vapor condition of such a fluid.

. andit is only through actual measurement oi the density of a mixture of the liquid and vapor that the operator may have any reliable knowledge as to the physical condition 01 the fluid stream at various points in the treatment.

It will be readily apparent to those skilled in the art that the continuous determination of the density of such a flowing stream is of tremendous importance and value to an operator in controlling the heating, mean density, time of detention in a given portion oi the circuit, etc. A continuous knowledge of the density of such a heated flowing stream is particularly advantageous where wide changes in density occur due to formation, generation, and/or liberation oi gases, with the resulting formation of liquid-vapor mixtures, velocity changes, and varying time of detention in different portions 01 the fluid path. In fact. for a fixed or given volume of path, a determination of the mean density in that portion provides the only possibility of accurately determining the time that the fluid in that portion of the path is subjected to heating or treatment. By my invention I provide the requisite system and apparatus wherein such information is made available continuously to an operator, and furthermore may comprise the guiding means for automatic control of the process or treatment.

While illustrating and describing my invention as preferably adapted to the cracking of petroleum hydrocarbon, it is to be understood that it may be equally applicable to the vaporization or treatment of other liquids and in other processes.

- In the drawings:

Fig. 1 is a diagrammatic representation of den sity measuring apparatus for a heated stream, and of mean density measuring apparatus of the stream through a portion of its flow path.

Fig. 2 is a. modification of a part of Fig. 1.

Fig. 3 is a. diagrammatic representation of a further embodiment of my invention.

Fig. 4 is a diagrammatic representation of the apparatus of Fig. 1 and including control provisions.

Fig. 5 is similar to Fig. 3 but illustrates pressure sensitive means.

Fig. 6 is similar to Fig. 1 but illustrates pressure sensitive means.

Referring now in particular to Fig. 1, I indicate a conduit l which may be considered as comprising the once through fluid path of an oil still where a portion of the path, such as the coil 2, is heated by a burner 3. After passing through the coil 2 the fluid is passed through a section of by the burner 3. The heating coil 2 will be hereinafter referred to as a first heating section, while variable area orifice I.

the coil 5 will be referred to as a second heatina section. In the preferred arrangement of the operation of the still the section 5 is the conversion or cracking section, and the one in which it is primarily desirable to continuouslydetermine the mean density of the fluid. After leaving the second heating section the fluid is discharged from the still through a conduit 6, comprising-in reality a section of the conduit l. I

In accordance with my invention I determine the density of the fluid atthe location 4 by causio If the orifice 1.

ing the fluid to pass through a variable area obstruction, such as an orifice "I, varying the area of the orifice 1 to maintain a constant differential thereacross, and determining the ratio of the weight rate of fluid fiow through the flow path to a function of the area of the orifice. Likewise the .density of the fluid at the location 6 may be determined from the ratio of the weight rate of fiuidflow to a function of the area of a through the second heating section 5 may be determined byaveraging the density of the fluid at the locations I and. 6. That the density of a flowing fluid may, be so obtained will be apparent from a conslderation ofthe matical development.

Let:- 7

following mathe- Wr=the weight rate of fluid flow Dr =density of the fluid at orifice I Do =density of the fluid at orifice I Dm =mean density across the second heating section 5 =Kr=difierential maintained across orifice 1 ho =Ko=diflerential maintained across orifice 8 Ar =area of orifice I The basic formula for an orifice is:

w=xcrsvfih and 1 The orifices I and 8 are shown as flat plates movable transversely in the sections 4 and 6 respectively to vary the free area of the orifice.

While I have found such orifices as illustrated,

and known in the art as segmental orifices to The mean density.

be satisfactory, it will be apparent that any other type of partial obstruction may be employed. The orifice I is positioned transversely in the section 4 to maintain a constant differential by means are reversible motor 0 ,under the control of a device such as a U-tube generally indicated at I and sensitive to the differential across the orifice I.

In-one leg of the U-tube I0 is a. float ll positioned in accordance with the differential across When the differential across the orifice I departsfrom a predetermined constant value thefioat llcloses an electric circuit causing the motor 9 to rotate in one direction or the otherand thus vary the area of the orifice I until the differential thereacross is restored to the predeterminedvalue.

The differential across the orifice 8 is maintained at a predetermined constant value by means of a similar device generally indicated at 12. The differential pressures maintained across the orifices I3, I andfl may be the same, or they may be different. So long as they are maintained at predetermined constant values,=di fi'erences in their absolute values may b properly compensated for in the design of the apparatus, as. will be evident to those skilled in the art.

To obtain a measure ofthe weight rate of fluid .fiow through the conduit l. I may emplo any known device for metering fluid flows.

In the embodiment of my invention disclosed in Fig. l

I have disclosed a meter of the rate otfiow similar to the devices I have described for maintaining a constant differential across .the orifices l and 8. From the Formula 1 given above it is apparent that if the headH across an orifice and the density D remains constant then .the weight rate of flow will vary as a functionof the orifice area A. The fluid before passing through the first heating section 2 is substantially constant in density and accordingly the orifice area across which a constant difierential pressure is maintained will be a measure of the rate of fluid flow.

Such changes .in density as may be encountered and which are usually given in terms of specific gravity may be properly compensated for in a manner hereinafter to be described.

In the conduit l ahead of the first heating section 2 I show avariable area orifice l3 across which a constant diflerential pressure is maintained by means of a U-tube, generally indicated at H controlling a motor l5. Assuming for ex- Cil by effecting energizatlon of the motor IS in proper direction to decrease the free area of the orifice. Upon an increase in the rate of flow to the conduit 1 the opposite action will occur, the motor l5 rotating in direction to increase the free area of the orifice to restore the differential thereacross to the desired value.

Further consideration of theFormula 1 above will indicate that if the density D and the area A are constant, then the flow through an orifice will vary as the square root of the differential pressure H. Accordingly, I may in place of utilizing a variable orifice, such as I have illustrated in Fig. 1, use the alternate arrangement shown in Fig. 2 where the device I4 is sensitive to the differential produced by a constant area orifice l6 which may be positioned in the conduit I in lieu of the variable area orifice H. A float H in one leg of the device M will accordingly be. positioned proportional to the differential pressure across orifice It. and

section 5.

'20 of a pilot valve 2|.

be of the type shown and described in United the motion thereof may be utilized to produce an 'efl'ect varying in accordance with the weight rate of flow through the conduit I as hereinafter described.

My invention contemplates producing a first measurable effect varying. in proper. functional relation to the weight rate of fluid flow, a second measurabl'eeffect varyingin proper functional relation to the areaof the orifice I, and a third measurable'effect varying in proper functional relation to the area of the orifice I; From the ratio between the first and second eflects I am able to determine the density of the fluid at the orifice I; from the ratio between the first and third effects the density of the fluid at the orifice 8 maybe determined. By further producing an effect varying as each of said ratios and determining the sum (and thereby the average) of the last named effects. I may obtain a measure of the mean density through the second heating section 5. In the embodiment of my invention shown in Fig. 1, I utilize 'fluid'pressures as the measurable effect," and through the agency of proper instrumentalities hereinafter to be described determine the'ra-" States Patent 2,054,464 to Clarence Johnson. Pressure fluid from a suitable source is admitted through a centrally located inlet port 22 and is so controlled that for every position of the valve.

stein 20 there will be a definite pressure established in the outlet port 23. Accordingly. as the follower i9 is angularly positioned, due to changes in position of the orifice l2, there will be a definite predetermined change in the fluid pressure at the outlet port 23. Briefly, therefore, for each positionof the orifice I! there will be a definite pressure established by the pilot valve 2|.

The cam section l8 may be properly shaped to correspond to the functional relation existing between the position of the orifice i2 and the fluid pressure which it is desired to establish by the pilot valve 2|. Thus referring to Formula 4 above, for example, it is apparent that the fluid pressure established by the valve 2| should vary as the square of the weight rate of fluid flow. Inasmuch as from Formula 1 it is apparent that the flow varies directly with the orifice area the cam section I! should be so shaped as to cause the fluid pressure established by the pilot 2| to vary as the square of the orifice area. The shape of the cam section It may be further warped to properly compensate for changes in experimental coefficient, approach factor,- and other factors varying in relation to orifice area.

To establish a fluid pressure varying in proper functional relation to the area of the orifice l, I provide an arrangement similar to that deorifice I provided with a suitably shaped camtt the" outlet port a of the pilot valve 21 will accordingly be-in proper functional relation to the position of the orifice I. Likewise I show the section 22, which through a follower 20 and pilot valve 3| establishes a fluid pressure at an outlet port 32 varying in proper functional relation to the position of the orifice 8.

The fluid pressure established by the pilot 2| is transmitted through a pipe 21 and branch I! 5 to a fluid pressure weighing device ll. The fluid pressure established by the pilot 21 is transmitted through a pipe 40 to a device 4| similar, to the device 32. The devices 39 and 4| bear against a fulcrumed lever 42 and impress thereon opposed v forces proportional to the magnitude of the fluid the-device 4| will be proportional to the pressure established bythe-pilot 21 multiplied by the distance the device 4| is from the fulcrum of the lever 42. Inasmuch as the forces produced by the devices 29 and 4| are opposed, the following mathematicalrelation will exist when the lever 42 is in equilibrium or neutral position:

- F3QX =F4l X b (7) where: I F=a=Force produced by device 39 F41=Force produced by device 4| a=Moment arm of device 39 b=Moment arm of device '4l 0 and:

but by construction: 7

F41 =f( l) a K =a constant therefore: I

I from (9) or:

l i b- D, (i0) From Equation 10 it is apparent that if the moment arm of the device 39 is maintained constant and the moment arm of the device 4| varied to maintain the lever 42in equilibrium, then the moment arm of the device 4| becomes a measure of the density of the fluid at the variable area orifice l.

To maintain the lever 42 inequilibrium or in neutral position I employv a pilot valve 43 having a movable stem 44 pivotally connected to the lever 42. The pressure established by the pilot 43 is effective for positioning the device 4| through a fluid pressure servo-motor diagrammatically illustrated at 46. Inpperation, assuming that the lever 42 is displaced in a counterclockwise direct on from the neutral position, theloadin'g pressure established. by thepilot 43 w'illimmediately decrease, causing the servo motor 46 to position the device 4| in a direction increasing the moment arm b until the increase in torque caused graduate the lever 42 to read directly in terms of density of the fluid at the oriflce' I. As the fluid pressure established by the pilot 4! and necessary to maintain the lever 42 in neutral position varies with the length of the moment arm b, it is apparent that the magnitude of this fluid pressure may be used as an indication of the density of the fluid. In Fig. 1 I have shown such an arrangement where a pressure sensitive Bourdon tube 41 is arranged to position an-index 48 relative to a scale 48, which may be graduated to read directly in terms of density.

It in lieu of the variable area orifice I8 the arrangement for obtaining a measure of the weight rate of flow shown in Fig. 2 is used, then the float I! may be arranged to operate a suitably shaped cam I8A so that the fluid pressure established by the pilot II will bear the desired functional relation to the rate of fluid flow through the conduit l. j

To obtain a measure of the density of the fluid at the orifice 8 I utilize an arrangement similar to that described for determining the density of the fluid at the orifice I. As shown in Fig. 1, the loading pressure established by the pilot II is transmitted through a branch conduit 58 to a fluid pressure weighing device 5|, and that established by the pilot II is transmitted through a pipe 52 to a fluid pressure weighing device 53. The devices 5| and 53 bear against a tulcrumed lever 54 in opposed relation and the moment arm 01' the device-53 is varied through the agency of a pilot valve 55 and fluid pressure operated servo-motor 56 to maintain the tulcrumed lever 54 in neutral position.

As demonstrated mathematically with reference to the determination of the density at the orifice I it may be shown that:

Accordingly by suitablygraduating the lever 54 I may obtain a'direct visual indication of the actuate a proximate or remotely located Bourdon tube 51 and index 58 to give an indication of the density relative to a scale 58.

From Equation 6 above it is apparent that the mean density of the fluid in the second heating section 5 is proportional to the sum of the loading pressures established by the pilot valves 43 and 55. In determining the mean density in the embodiment of my invention shown in Fig. l I establish a fluid pressure proportional to the sum of the said two loading pressures and utilize the latter pressure to actuate a suitable exhibiting means. I obtain this latter fluid pressure which is proportional to the sum of the two loading pressures through the agency of a device generally indicated at 60 and illustrated and described in United States Patent 2,098,913 to P. S. Dickey.

The loading pressure established by the 'pilot 43 is transmitted to a chamber 61, whereas that established by the pilot 55 is transmitted to a chamber 82. Each of the chambers 8| and 82 has one wall, consisting of a pressure sensitive diaphragm which diaphragms are connected together for simultaneous movement by a member 88. The force tending to move the member 88 downward will therefore be proportional .to the sum of the pressures within the chambers 8| and 52. The member 53 is arranged to actuate, by means of a iulcrumed lever 54, afluid pressure supply valve 55 or an exhaust valve 88 when I moved. from the neutral position in which it is density of the fluid at orifice location I, or at shown. The valves and 65 control the admission and discharge of pressure fluid from a chamber 51, which is separated from the chamber 82 by the pressure sensitive diaphragm. Accordingly the member 53 is urged upwardly by a force proportional to the magnitude of the pressure within the chamber 51.

When the fluid pressure within the chamber 81 is equal to the sum of the pressures within the chambers SI and 62 the supply and exhaust valves 55 and 66 will be closed, whereas if the pressure 51 is less than that within chambers SI and 52: the supply valve 65 will be opened until the pres-., sure within chamber 51 has increased to again be equal to the sum of the pressures within chambers 8| and 62. Conversely, if the pressure within chamber 51 exceeds the sum of the pressures within chambers 8| and 52, then the exhaust valve 55 will be opened until the pressure within chamber 61 has been reduced sufliciently to restore equilibrium.

Due to the action of the device 60 the pressure within the chamber 51 will continuously stand in direct proportion to the sum of the densities of the fluids at the orifices 1 and 8, and accordingly its magnitude may be taken as a measure of the mean density of the fluid within the second heating section 5. To obtain a visual indication of the magnitude of the pressure within chamber 61, I show connected thereto a pressure sensitive Bourdon tube 58 arranged to position an index 59, which may be provided with a stylus to record the mean density on a suitably graduated time rotatable chart l0 and to indicate the same relative to a graduated scale II.

It will be understood that the indicating and recording arrangement I have shown is intended to be merely diagrammatic and that I may employ other devices for obtaining a visual indication of the pressure with the chamber 61 as will be apparent to those skilled in the art. It will be further apparent that I may utilize the pressure established within the chamber 81 to control the processing of the fluid through the heating sections 2 and 5 through the agency of suitable instrumentalities.

Referring to Fig. 4 I show therein the Bourdon tubes 41, 51 and 68 arranged to position respectively the pilot valves I21, I28 and I29 establishing loading pressures representative respectively of fluid density at the orifice l, fluid density at the orifice 8, and mean density of the fluid in heating section 5. The loading pressures are selectively efiective, through the agency of valves I80, I1, I32, I33, in regulation of the control valves I34 and I35. The valve I34 controls the rate of supply of fluid to the treating system while the valve I35 controls the heating burner 3.

Thus the treatment of the fluid may be in accord ance with a determination of or manifestation of orifice location 8, or of the mean density of the fluid between the oriflce locations 1 and 8.

By proper manipulation of the valves I38, I 3|,

I I32 and I33 I may control the rate of charge from density at 1, or at 8, or the mean; and control the tion is in stable. form, such changes in density as.

occur are usually of minor magnitude and do not appreciably affect the accuracy of measurement. However, if such changes in'density, which are usually reduced to changes in specific gravity,

are of suflicient magnitude to materially afiect the accuracy of the measurements of the rate of flow I may provide the apparatus di'sclosed in Fig. 1 with suitable means for correcting for such changes in density. As an example, I have shown the device 38 manually adjustable along the lever 42 so that the moment arm (a) may be varied in suitable functional relation to changes in density to properly correct therefor. I have shown a manually adjustable screw 12, which may be used to position the device 39 so that an index carried thereby corresponds to the density or specific gravity reading given on a suitably graduated scale 13. The density of the fluid within the conduit l ahead of orifice [3 may be periodically determined by a hydrometer or other Well-known means and then the device 39 adjusted so that the force produced thereby on the beam 42 is suitably compensated for changes in the density or departure of the actual density from the density for which the device was designed.

Likewise the device 5| may be arranged so that changes in initial specific gravity are properly compensated for by means of a manually adjusted screw 14 and scale 15. 1

In Fig. 3 I have illustrated a further embodiment of my invention wherein the effects which are established in accordance with the areas of the orifices 1,' 8 and I3 are periodic electric imtaining periodic simultaneous impulses of a time duration proportional to the logarithm of a function of the area of orifices l3, 8 and 1. Bearing against the cam shape l8 of the orifice H, for example, is a follower ISA operating a contact 18 connected to a suitable source of current 11. Arranged to periodically engage the contact 16is a cam 18 intermittently operated by a motor diagrammatically illustrated at 19. The intermittent operation of the motor 19 is obtained by means of a contact drum 88 continuously rotated at constant speed by means of a motor 8|. The drum 88 carries a conducting segment 82. During a portion of each revolution of the drum 88 the conducting segment 82 will permit the motor 19 to be energized from the source 11 as an inspection of Fig. 3 will make evident. The length of the segment 82 is suilicient to cause one complete revolution of the cam 18. Accordingly, the normal position of the cam 18 is that shown in v the drawing, and upon energization of the motor 18 the cam 18 will be rotated through one complete revolution. Through the use of self-starting synchronous motors the cam 18 may be made to rotate at a uniform rate of speed as will be apparent to those skilledin the art.

During each revolution of the cam 18 the contact 16 will be engaged for an increment of time determined by the shape of the cam section 18 and the cam 18. Through suitably shaping these surfaces the duration of the engagement between contact 18 and cam 18 may be made proportional to the logarithm of (Wr) Thus the cam section l8 may be such that the position of the contact 16 will be directly proportional to the said logarithm so that the cam 18 will have a uniform rise, orthe logarithmic function may be partially obtained through shaping of the section I8 and the tained through shaping of the cam 18. Regardless of the exact arrangement which may be em ployed the desideratum is to have the contact 18 engage the cam 18 periodically for an increment of time proportional to the logarithm of (We Simultaneous with the energization of motor 18 similar motors 83 and 84 are operated to r0- locations 4, 6, and the mean density of the fluid v within the second heating section 5. In comparing the time durations of the impulses I employ the principle of logarithms that I may obtain a ratio through determining the difference in time lengths of the impulses. For example, in determining D: in accordance with Formula 4 above I obtain periodic impulses proportional in time length to the logarithm of We and periodic impulses of a time length proportional to g/(AI).

Each periodic impulse proportional to W1 is the mean density ofthe fiuidfwithin the second heating section 5 may be obtained by suitably adding corresponding impulses propor tionlal f in time length to D: and Do.

I will now describe the means I employ for obtate cams 85 and 88 through one revolution. As described with reference to the orifice I3, cam sections 28, 29, and cams 85, 88 may be suitably shaped so that in the case of the cam 85 an electric impulseofa time durationproportional to the logarithm of I(Ar)' will be obtained through engagement of the cam 85 with a contact; 81 and similarly an electric impulse of duration proportional to the logarithm of 'f(Ao) will be obtained through engagement of the cam 88 with a contact 88. I r

To obtain now a determination of the ratio of the weight rate of flow of fluid to HA1), I efiect movement of a member proportional to the difference in time length of the impulses originated by the cams 18 and 85. 'Engagement of the cam 18 with the contact 16 serves to energize a winding 88 of a self-starting synchronous motor 81 windings- 88 and 82 are deenergiz ed. However,

when either winding 98 or 82 alone is energized, then the motor 82' willbe urged to rotation'in a direction depending upon the particular winding energized. Thus energization of the winding 99 may effect rotation in a counterclockwise direction, whereas energization of the winding 92 may eiiect rotation in a clockwise direction. As the differenc in energization of the windings 99 and 92 is proportional to the difference in logarithms it is apparent that the motor 9| will rotate for an increment of time proportional to that diflerence. Accordingly, a member such as the member 93 positioned by the motor 9I will be periodically moved from the initial Position, in which it is shown, for an increment 01 time and likewise for a distance proportional to the said diflerence. It the time duration of the electric impulses originating through the agency of the cams I9 and 95. are equal, then the member 93 will remain in the initial position. It the impulse established by the cam I9 is of longer duration than that established by the cam 95 then the member 93 will be .moved in one sense from the initial position and if the impulse established by the cam 95 is the longer then the member 93 will be moved in opposite sense from the initial position. When the member 93 remains in the initial position throughout a complete cycle of operation of the cams I9 and 95 it indicates that a ratio of 1 exists between WP and ,f(Ar) or that the logarithm of the ratio is zero. Displacement of the member 93 to the left of the initial position as viewed in the drawing indicates a ratio less than 1, or a negative logarithm. Movement of the member 93 to the right or the initial position indicates a ratio greater than 1 or a positive logarithm.

The member is driven by the motor 9i through a friction clutch so that subsequent to each advancement from the initial position it may be returned thereto to obtain an impulse varying in direct proportion to the ratio of We to flA'r). Disposed on either side of the member 93 and in operative relation thereto are proper- 1y shaped cams 94 and 95 periodically rotated through one revolution subsequent to each advancement of the member 93 by a motor 96. Proper sequential operation of the cams 94 and 95 relative to the operation of member 93 is obtained through drum 99 and a conducting segment 9I thereon.

Subsequent to each cycle of operation of the motors I9 and 99 the motor 96 is energized by means of segment 91, which is of such length that cams 94 and 95 are rotated through one complete revolution and then remain stationary until a further cycle of operation of motors I9 and 93 occurs. When member 93 is displaced to the left, the cam 94 will act to restore it to the initial position, and when displaced to the right, cam 95 will act to restore it to the initial position. The operation of the parts of the apparatus so far described is such that periodically the member 93 will be displaced from the initial position an amount proportional to the logarithm of the ratio of the weight rate of fluid flow to f(Ar) and subsequent to such displacement the member 93 will be restored to the initial position through the agency 01' cams 94 and 95, which cams are properly shaped so that the time engagement with the member 93 will be proportional to the antilogarithm of the said logarithm.

The cam 95 is provided with a short dwell section at its point of maximum rise, so that if the member 93 remains in the initial position because of a ratio of one existing between W2 and {(Ar) it will engage the member for a corresponding increment of time, in this case the cam 94 by virtue of its shape will only momentarily engage the member. Improper engagement between the cam and member 93 is prevented when the member 93 is displaced to the left by having thecam 94 follow the cam 95 so that after such displacement to the left it will not be restored to the initial position until after the dwell of cam 95 has passed.

The member 93 carries a contact 99 which engages the cams 94 and 95 and serves to originate an electric impulse proportional to the said antilogarithm. This electric impulse serves to periodically energize a winding 99 of a self-starting synchronous motor I99 and to cause displacement of a contact member I 9|, driven thereby through a friction clutch, from an initial position an amount proportional to the magnitude of the antilogarithm.

Following each advancement of the contact member I9I proportional to the antilogarithm of the logarithm of the ratio of W1 to HA1) I produce a further advancement thereof proportional to the antilogarithm of the logarithm of the ration of W1 to f(A0) and thereby move the contact member I9I during each cycle of operation an amount proportional to the sum of said ratios, or as evident, proportional to the mean density of the fluid within the second heating section 5. I obtain this subsequent advancement of the contact member I9I through apparatus similar to that described for obtaining the initial advancement. 'I'h'us engagement of contact IS with cam I8 serves to energize a winding I Hot a motor I93 having an opposed winding I94. Engagement of the contact 98 with the cam 99 serves to energize the latter winding. The diii'erence in time duration of the energization of windings I92 and I94 serves to position a movable member I95 from the initial position shown. The displacement of the member I95 occurs simultaneously with the displacement of the member 93. However, during that part of the cycle of complete operation when member 93 is being returned to the neutral position, and hence establishing an impulse eilfective i'or positioning the contact member IN, the member I95 remains stationary. When, however, the member 93 has been restored to the initial position the member I95 will be restored to its initial position through the agency of cams I99, I91 which are rotated by'a motor I99 periodically energized through a conducting segment I99 oi the drum 99. It will be evident that the member I05 will be restored to the initial position subsequent to such restoration of the member 93, due to the fact that the segment I99 follows the segment 91.

The cams I98 and I9! act in the same way as the cams 95 and 94 respectively and periodically establish an electric impulse proportional to the antilogarithm of the logarithm of the ratio of the weight rate of fluid flow to (A0). The electric impulses established through engagement of the contact member I95 with either the cams I96 or I91 act to cause a further displacement of the member I9I. Thus for each cycle of operation of the earns 94, 95 and I96, I91 the member I9I will be advanced an amount proportional to the sum and hence the mean of the ratios determined by the apparatus described, or expressed mathematically:

where A1o1=Periodic displacement of member IOI.

To provide a visual indication or record of the displacement of the member IN, I provide means for restoring it to the initial position subsequent to each advancement, and in so restoring it originating an electric impulse of a time duration proportional to its displacement and thence utilizing such impulse to control the positioning of a suitable member, such as that index H0.

After operation of the motor I08 further rotation of the drum 80 causes segment III to'energize a motor H2 for a length of time suflicient to cause a complete revolution of a cam H3 from the normal position shown. In the rotation of cam H3, a cam follower H4 will engage the contact member IM and return it to the initial position. rise thenthe time duration of such engagement between the members IOI and H4 will be proportional to the displacement of the member I M from the initial position. members IOI, H4 energize a winding H5of a reversible motor H6.

Simultaneously with the energization of motor H2 a motor H1 is energized for a sufficient length of time to cause a cam I I8 rotated thereby to pass through one complete revolution. During a part of each revolution of the cam H8 a con tact member H9 is engaged for a time duration proportional to its position. Such engagement of the cam H8 with the contact member H9 energizes a winding I20 of the motor H6. As the cams H3 and H8 rotate in phase the motor H6 will rotate in one direction or another for an increment of time proportional in duration to the difference in time length of energization of the winding I I5 as compared with the winding I20. Thus if the time duration ofenergization of winding H5 is greater than that of. the winding I20, then the motor H6 will rotate in a If the cam H3 is of uniform.

Engagement of counterclockwise direction an amount proportional to the difference in time length of energization. Conversely, if the winding I20 is energized for the longer increment of tim then the motor H6 will rotate in a clockwise direction.

The motor H6 positions, through a suitable linkage arrangement, a fulcrumecl lever I2I about a fixed fulcrum I22. Thelever I2 I positions the index H0 relative to' a time rotatable chart I23 .which may be drivenby any suitable clock mechanism (not shown) so that a record of the mean density relative to time will beinscribed thereon. Also coo'perating with the index 5 I I0 is a suitably graduated scale I24 whereby the instantaneous mean density is continuously indicated. The contact member I I9 normally rests againstthe lever I2I and is pivoted at the fulcrum I22. Its normal position therefore corresponds to the position of the index H0 and the time duration of the electric impulses formed by engagement of the cam I I8 with the contact member H9wili be proportional to the position of the index H0. 7

Those contacts formed by engagement of the contact member H4 with the arm" IOI are propor-' tional in time duration to the mean density of the fluid in the second heating section 5. Accordingly it may be said that the motor H6 compares the time duration of the impulses formed through engagement of cam I I8 with contact member I I9, and those formed by engagement of contact member H4 with arm IOI; and then varies the time duration of the former to bring them to the same in the second heating section 5, it may readily be utilized to determine only the density of the fluid at the orifice 8 or at the orifice 1. Thus in the conductor leading to the motor I00 from the cams I06--I0'I I show a manually operable switch I25. By opening this switch to the position shown in dotted line the motor I00 will only be periodically energized through engagement of the cam 94 or cam 95 with the contact 98. Accordingly, the index H0 will be positioned to correspond with the time duration of the impulses formed by such engagement, or to correspond with the density of the fluid at the orifice 1. Similarly I show in the conductor from cams 94, 95 to the motor I00 a manually operable switch I26 which, it moved to the open position as shown in dotted line, will cause the motor I00 to be energized solely through engagement of cam I06 or cam I01 with contact arm I05, and accordingly the indicator will then be positioned solely in accordanoe with the density at the orifice 0.

While I have illustrated my invention adapted to determine density at a point remote from a reference point or the mean density between ,two points remote from a reference point, it will be evident that it may be adapted to other uses and that in general the apparatus is capable of determining the ratio between any two variables or the mean between any two variables; that while in the embodiments shown means are provided for correcting the meter of the weight rate of flow for changes in density, the apparatus will, notwithstanding that density determinations of the fluid are impossible, indicate the change in density between the metering or reference point and thepoint or points remote therefrom.

In Figs. 5 and '6' I have followed the general arrangements of Figs. 3 and l respectively, but have shown that Bourdon pressure sensitive tubes I36, I31 and I38 may be substituted forthe pressure differential devices of Figs. 3 and 1. Such Bourdon tubes may be sensitive to fluid pressures in the same or in different fluid treating systems or may be a part of a temperature measuring system. Thus I disclose fully the application of my invention to the determining of the ratio, average, sum or mean of any two variables. Naturally the control'provisions of Fig. 4 are equally adaptable essing, or working of other fluids, such for example, as in the vaporization'of water to form steam.

This application constitutes a continuation-inpart of my co-pending application Serial No. 193,333, flled March 1, 1938, and now Patent No. 2,217,642, dated'October 8, 1940.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

1. In an apparatus for determining the ratio between two variables, in combination, a movable member, means periodically moving said member from an initial position a distance proportional to the difference in the logarithms corresponding I to the magnitude of each of said variables, a cam having an antilogarithmic contour, means for periodically rotating said cam at a constant rate of speed thereby restoring said movable member to the initial position after each displacement therefrom and engaging said movable member for an increment of time proportional to the antilogarithm of its displacement from the initial position, and means for exhibiting the time duration of the engagement of said member with said cam.

2. In an apparatus for determining the ratio between two variables, in combination, a movable member, means periodically moving said member from an initial position for a period of time proportional to the difference between the logs.- rithms corresponding to the magnitudes of said variables, means for periodically restoring said electric impulses of a time length proportional to the logarithm of the other of said variables, means periodically originating electric impulses of a time duration proportional to the antilogarithm of the difference in time lengths of said first two named series of periodic impulses, and indicating means positioned in accordance with the time duration of said last named impulses.

4. In a telemetric transmitter for periodically originating electric impulses of a period of time proportional to a function of a variable having a zero magnitude for a finite value of the function, comprising in combination, a movable member periodically moved from an initial position in an amount proportional to the magnitude of the variable and in sense dependent upon the algebraic sign of the variable, a first cam for periodically restoring said movable member to the neutral position when displaced from th initial position in one sense, a second cam for periodically restoring said movabl member to the initial position when displaced from the neutral position in opposite sense, and contact means controlled by said cams and member for originating an electric impulse proportional in time length to the time required for said cams to restor said movable member to the neutral position.

In a telemetric transmitter for periodically originating electric impulses of a period of time proportional to a function of a variable having a zero magnitude when the function of the variable is not equal to zero comprising in combination, a movable member adapted to be periodically displaced from an initial position an amount corresponding to the magnitude of the variable and in sense dependent upon the Sign of the variable, a cyclically operated cam for restoring said movable member to the initial position subsequent to each periodic displacement disposed on either side of said member, one of said cams shaped to correspond with the functional relation existing between said variable and function when said variable is positive and the other of said cams shaped to correspond with the functional relation existing between said variable and function when said variable is negative,

and circuit controlling means operated by the joint action of said cams and member.

8. Apparatus for controlling a fluid treating system having a forced circulation path to one end of which the fluid is supplied under pressure. comprising in combination, means for heating the fluid path, means cyclically telemetering a fi signal ha ing a characteristic corresponding to the logarithm of the weight rate of fluid flow through the heated fluid path, a variable area oriflce in said fluid path located at a reference point subsequent to the entrance to the path, means for varying the area or said oriflce to maintain a predetermined differential pressure thereacross, means cyclically telemetering a second signal having a characteristic corresponding to the logarithm of the area of said oriflce, means, for determining the difference in characteristic of said signals, and means positioned by said last-named means for controlling the heating means of said fluid path.

7. Apparatus for controlling a fluid treating system having a forced circulation path to one end of which the fluid is supplied under pressure, comprising in combination, means for heating the path, means cyclically telemetering a first signal'having a characteristic corresponding to the logarithm of the weight rate of fluid flow through the heated fluid path, a variable area orifice in said heated path through which said fluid flows located at a reference point subse-,

quent to the entrance to the path, means for varying the area of said oriflce to maintain a predetermined differential pressure thereacross, means cyclically telemetering a second signal having a characteristic corresponding to the logarithm of the area of said oriflce, means for determining the difference in characteristic of said telemetered signals, and means positioned by said difference in characteristic of said signals for controlling the rate of fluid supply to the sure thereacross, means cyclically telemetering a second signal having a characteristic corresponding to the logarithm of the area of said orifice, means for determining the difference in characteristic of said signals, and means positioned by said difference in characteristic of said first and second signals for controlling the treating of the fluid in the path.

9. Apparatus for controlling a fluidtreating system having a forced circulation path to one end of which the fluid is supplied under pressure, comprising in combination, means for treating the fluid as it flows throu h said path, means cyclically telemetering a flrst signal having a time duration corresponding to the logarithm of the weight rate of fluid flow through the treated fluid path, a variable area oriflce through which the treated fluid flows located at a reference point subsequent to the entrance to the fluid path, means for varying the area of said oriflce to maintain a predetermined diflerential pressure thereacross, means cyclically and simultaneously with said first signal telemetering a second signal having a time duration corresponding to the logarithm of the area of said orifice, a receiver responsive to both of said signals and positioned in accordance with the antilogarithm of the difference in time duration of said first and second signals, and treatment control means positioned by said receiver.

10. In a measuring apparatus of the type having means responsive to a variable such as for example, fluid rate of flow, pressure, or theiike, including a telemetric system of the time electric impulse typ the improvement comprising a first transmitter having means sensitive to the value of a first variable, means cooperating with the first named means periodically originating electric impulses of a time duration varying in logarithmic relation to the value of the first variable,

a second transmitter having means sensitive to the value ofa second variable, means cooperating with-the second transmitter means periodically originating electricimpulses of a time duration varying in logarithmic relation to the value of the second variable, and receiving means.

accumulating and integrating said periodic impulses providing a manifestation of the relation between the two variables.

11. Control apparatus including in combine tion, means producing periodic electric impulses 

